1. Field of the Invention
The present invention is directed to a connector system for mechanically and electrically connecting a lead in a medical device for delivering electrical energy to a body site from an implantable source for the electrical energy, such as for connecting a pacing lead to an implantable pulse generator in an implantable pacing system.
2. Description of the Prior Art
In implantable medical devices, which are for the purpose of delivering electrical energy to a body site, such as the heart, a flexible lead is used to conduct the electrical energy from an implanted source of the electrical energy to the body site. The lead delivers the electrical energy at a free end thereof. The opposite end of the lead must be mechanically and electrically connected to the housing containing the source of electrical energy. Since the system is intended for in vivo implantation in a patient, the connection system in such devices must not only provide reliable mechanical and electrical connection, but also must do so in a manner which does not significantly add to the size of the implanted system, and which seals from body fluids the actual location at which the electrical connection occurs.
In the case of a heart pacemaker, for example, the lead may be used to carry conductors which serve a purpose other than delivery of the therapeutic electrical energy. For example, in sophisticated pacemakers of the type currently available, one or more sensors may be disposed in the pacing lead for detecting various physiological characteristics. Each sensor has at least one conductor associated therewith which must be contained within the pacing lead and also electrically connected to an appropriate contact at the housing, so that the electrical signals corresponding to the sensed physiological characteristic can be used by logic circuitry within the housing to control the pacing rate, the amplitude and duration of the pacing pulses, and other attributes of the pacing therapy.
It is a problem in the implantable medical device technology to provide a reliable mechanical and electrical connector which can accommodate a relatively large number of electrical contacts without significantly adding to the size of the connector.
A further problem in the implantable medical device technology is to minimize the insertion force required to insert the lead plug into the housing socket. Typically, a lead is by design very flexible and the lead plug on the lead does not protrude much beyond the pacer body when the lead is inserted into the housing socket. Accordingly, it is rather difficult to insert the flexible male lead into the female connector. Compounding the problem in multiple contact systems is the high insertion force required due to the accumulated resistive effects of spring contacts and fluid isolation seals.
Various types of connector or plug assemblies (not necessarily for implantable medical devices) are known in the art which make use of a resilient or deformable component within the assembly to effect electrical connection of other components. For example, a multicontact connector is disclosed in U.S. Pat. No. 2,749,526 wherein the plug and socket connector elements have complementary conical shapes, and the contacts are in the shape of barbs so that a relatively large contact area is presented by each contact for mating with its counterpart. The contacts are held in elastic plug and socket members, so that the elements can be tightened together sufficiently to insure proper electrical connection. A compression joint for an electrical connector which is also deformable when the two connector elements are tightened together is disclosed in U.S. Pat. No. 2,829,357.
Switches having deformable, elastic contact elements with electrically conductive particles embedded therein are disclosed in U.S. Pat. Nos. 3,509,296 and 3,952,173. When the contact elements are compressed and deformed, the particles move closer together causing the element to become conductive, or increase in conductivity.
A snap-together universal electrical connection is disclosed in U.S. Pat. No. 4,978,306, wherein a spherical plug is snapped into a spherical socket so as to rotate and swivel therein. Contact elements are disposed at selected locations on the respective surfaces of the plug and socket so that electrical connections are made and broken as the plug is moved within the socket.
A cable connector is disclosed in U.S. Pat. No. 2,824,183 having two pairs of contact elements which are normally maintained spaced apart by resilient concave walls in which the contact elements are respectively mounted. The contact elements so mounted are contained within a socket, with the contacts being forced together by the insertion of a plug in the socket, the prongs of the plug causing the elastic walls to deform and force the contacts together.
A connector is disclosed in Japanese Application No. 62-29634 wherein a male connector element has a number of axially extending flexible carriers each having a contact at a free end thereof. The carriers surround a circular plate movable by a pusher rod. The male connector element is loosely inserted in a female connector element, and the rod is pushed so that the plate causes the carriers to move radially outward, forcing the contacts into connection with corresponding contacts carried on the interior of the female connector element.
A switch assembly is disclosed in German OS 31 37 288 wherein a resilient ball element is contained within a housing, the ball element containing particulate electrical conductors. When an actuator element is pressed, the ball is flattened so that its circumference touches a cylindrical contact surrounding the ball. The particulate conductor embedded within the ball thereby causes an electrical connection to be made.
Lastly, a locking electrical outlet plug is disclosed in U.S. Pat. No. 2,049,093, wherein the plug has an actuator rod with a free end that is inserted into the socket adjacent one of the blades of the plug. After the plug is inserted in the socket, the actuator can be pushed to force the free end tightly between the plug blade and a wall of the blade receptacle in the socket to hold the plug tightly in the socket. The actuator can be released when removal of the plug is desired.
None of these known types of plug assemblies is specifically designed or intended for use in an implantable medical device, such as a heart pacemaker. Therefore, none of these known devices address the problems associated with implanted medical devices of maintaining a small size while accommodating a large number of contacts and being impervious to, and isolated from, the action of body fluids, and of achieving reliable long-term electrical and mechanical connections with a small insertion force.